I was trying to update from 12.04 to 14.04 but I encountered an issue where the upgrade could not be calculated.

[Armando Nunez]

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ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: update-manager 1:0.156.14.13
ProcVersionSignature: Ubuntu 3.2.0-60.91-generic-pae 3.2.55
Uname: Linux 3.2.0-60-generic-pae i686
ApportVersion: 2.0.1-0ubuntu17.6
Architecture: i386
Date: Tue Apr 22 14:13:15 2014
GsettingsChanges:
 com.ubuntu.update-manager first-run false
 com.ubuntu.update-manager launch-time 1398195503
 com.ubuntu.update-manager window-height 748
 com.ubuntu.update-manager window-width 615
InstallationMedia: Ubuntu 12.04 LTS "Precise Pangolin" - Release i386 (20120423)
MarkForUpload: True
PackageArchitecture: all
ProcEnviron:
 TERM=xterm
 PATH=(custom, no user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: update-manager
Symptom: ubuntu-release-upgrader-core
UpgradeStatus: Upgraded to precise on 2014-04-22 (0 days ago)